(a) Field of the Invention
The present invention relates to a liquid crystal display, and more particularly; to a common voltage generator of a liquid crystal display.
(b) Description of the Related Art
Typically, a liquid crystal display (LCD) includes two display panels having pixel electrodes and a common electrode, and a dielectric-anisotropic liquid crystal layer interposed between the two display panels. The pixel electrodes are arranged in a matrix configuration with rows and columns and are connected to switching elements such as thin film transistors (TFTs) such that data voltages are sequentially applied to rows of the pixel electrodes. The common electrodes are formed to cover an entire surface of the display panel, and a common voltage is applied to the common electrode. In a circuit diagram, the pixel electrodes, the common electrode, and the liquid crystal layer interposed therebetween form a liquid crystal capacitor, and the liquid crystal capacitor and the switching element connected to the liquid crystal capacitor serve as a basic unit of a pixel.
In the liquid crystal display, an electric field is formed in the liquid crystal layer by applying voltages to the two electrodes, and light transmission through the liquid crystal layer is controlled by adjusting the intensity of the electric field in the liquid crystal layer. Accordingly, a desired image is obtained. Often, the polarity of the data voltage with respect to the common voltage is inverted every frame, every row, or every pixel to prevent device deterioration that may result from applying the electric field to the liquid crystal layer in one direction for a long time.
The liquid crystal display includes a liquid crystal panel assembly that has pixels each having a switching element and display signal lines connected to the pixels, a data driver that applies corresponding data voltages to the pixels through the switching elements, a gray voltage generator that generates gray voltages and supplies the gray voltages to the data driver, and a common voltage generator that supplies the common voltage to the liquid crystal panel assembly.
A problem with the liquid crystal display is the formation of a parasitic capacitance between the gate and the drain of each switching element. Formation of the parasitic capacitance causes coupling of the common voltage with the data voltage, which results in the common voltage becoming higher or lower than the intended voltage. Therefore, a direct current is applied in the form of an alternating current, and different voltages are applied to the pixels. When the difference in the voltages applied to the pixels becomes large enough, stripe-shaped horizontal crosstalk is displayed on a screen. It is desirable to eliminate this horizontal crosstalk, as it deteriorates image quality.